Ledermann
DENSITY DETERMINATION:
The study of chemistry involves not only observing changes in matter, but also measuring those changes.
In fact, most chemical principles cannot be fully understood without obtaining and analyzing some
quantitative data.
Careful attention should be given to the degree of uncertainty in your measurements. Record only those
digits which are significant, and use only those digits in your calculations. The accuracy of your methods
can be reported with your results in terms of percent of error. The percent error in calculations and
measurements is a comparison of the differences between experimental results and theoretical values,
expressed as a percentage. Percentage error can be determined as follows:
% error =
experimental value – theoretical value
theoretical value
X 100
A useful way of comparing substances is to compare their densities. By carefully measuring the mass and
volume of two substances, their densities can be calculated as follows:
density =
mass
volume
OBJECTIVES
 Determine the density of different substances from mass and volume measurements.
 Calculate the percentage error in your results.
EQUIPMENT
graduated cylinder (50 ml or 100 ml)
electronic balance
beaker (50 ml or 100 ml)
ruler
fishing line attached to a rubber stopper
PROCEDURE
A. Density of Water
1. Using a clean small beaker, obtain about 30 ml of distilled water.
2. Place your 50 ml or 100 ml graduated cylinder on the electronic balance and RE-ZERO the balance.
3. With your graduated cylinder on the balance, slowly add distilled water until you have approximately
20 g of water in the graduated cylinder. Record the mass of the water to the nearest 0.01g. Do NOT
dump the water out!
4. Take the graduated cylinder with the water, to your lab table. Read the bottom of the meniscus as
shown in Figure F-1. Record the volume of the water on your answer sheet to the nearest 0.1 ml.
Then pour the water in the sink.
Figure F-1. Reading liquid volume.
B.
Density of a Solid
1. Obtain a rubber stopper from your teacher and measure its mass. Record the mass on your
answer sheet to the nearest 0.01g.
2. Fill a 50 ml or 100 ml graduated cylinder about one-half full of tap water and read the
volume to the nearest 0.1 ml.
3. Carefully immerse (dunk) the solid in the water in the cylinder. Read the new volume to
the nearest 0.1 ml.
4. Calculate the volume of the object and record it to the nearest 0.1 ml.
5. Return the solid to a container designated by your teacher and pour the water in the sink.
C. Density of an unknown solid
1. Choose a metal block from the front counter.
2. Find the mass of the block to the nearest .01 grams and record it.
3. Use the formula length x width x height to determine the volume of the cube. Measure the
length, width, and height in cm using a ruler. Measure to the nearest .01 cm.
4. Calculate the density of the block.
5. Try to identify your block with the information on the table below.
6. If there is time, try to identify a different block.
Substance
Aluminum
Brass
Copper
Iron
Nickel
Density
2.7 g/cm3
8.4 g/cm3
8.9 g/cm3
7.8 g/cm3
8.9 g/cm3
Substance
Zinc
Magnesium
Lead
Gold
6.9
1.78
11.4
18.9
Density
g/cm3
g/cm3
g/cm3
g/cm3
Ledermann
NAME
DENSITY DETERMINATION:
____________________________________
ANALYSIS
1. Use the data collected in Parts A and B to calculate the mass per unit volume density for water and
the unknown solid. Remember Density = mass/volume
PART
A
MASS
Mass of Water = _____________ _______
NUMBER
B
LABEL
Mass of solid object= ____________ ______
NUMBER
C
LABEL
Mass of block____________ ________
Number
Volume
Density
___________ ______
_________ ______
NUMBER
LABEL
___________ ______
NUMBER
LABEL
NUMBER
LABEL
_________ ______
NUMBER
LABEL
Volume of block ________________ _________
label
number
label
Density of block (Show your calculations!)____________________
Identity of the block. We believe the block is made out of _____________________ because…
CONCLUSIONS
1. Using the formula in the introduction of this lab, calculate the percentage error, for Part A of your
results. The theoretical density is 1.00 g/ml.
Percent error =
2. What are the major sources of error in Part A of your experiment?
3. The method used to find the volume of the solid in part B will not work for all solids. What are some
(2 or 3) problems that could arise that would require you to use a different method to find the volume
of the solid?



 Suggest an alternate method of determining the density for a solid with one of the problems that
you described above.